I hav a 1994 4.0L OHV XLT Ranger w/ a lil over 128,000 miles on it, and someday when I get the money i'd like to run a Eaton M90 Super-Charger on it, I know I'll hav to rebuild the motor to handle the power of the super charger. Thus my question is would this rebuild kit from Rock Auto be "Heavy-Duty" enough to handle the Eaton M90's Power?

well brother, it would almost be cheaper to swap out to a V8, you'd get more power and MPG's. your looking at getting around 300 HP with the super charger on there (of course depends on the amount of boost) but, a fine tuned 5.0 V8 will pull those same numbers. in the end just figure which one is cheaper.